Catheters with an expandable member, such as a balloon, are used to treat body lumens that have been occluded or weakened by disease. In angioplasty, for example, a catheter is threaded through the vasculature to locate the balloon at the site of an occlusion where the balloon is inflated to dilate the lumen. To maintain the lumen in a dilated condition, a tubular endovascular prosthesis may be provided at the site. The prosthesis is placed over the balloon such that, when the balloon is inflated, the prosthesis is expanded into contact with the wall to hold the lumen open. To treat aneurysms, a graft may be provided over the balloon. The ends of the graft are attached to healthy portions of the lumen on either side of the aneurysm so that the body of the graft bridges the weakened area.